• Korean Journal of Materials Research
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• v.14 no.1
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• pp.67-72
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• 2004

The glass-forming conditions are investigated in the $K_2$O-CaO-$SiO_2$ $-P_2$$O_{5}$ system with 10~65 mole% of$ P_2$$O_{5}$. Thermal properties and dissolution properties were investigated according to variation of the SiO and KO contents in selected compositions. The glass formation condition was determined when $K_2$O/$P_2$$O_{5}$ mole ratio 0~0.24, $SiO_2$/($SiO_2$+$P_2$$O_{5}$ ) mole ratio 0～0.29, and CaO/$P_2$$O_{5}$ mole ratio 0~1.00. In the result of the thermal properties, the glass transition temperature($T_{g}$) and softening temperature($T_{s}$ ) were gradually shifted to the lower temperature range with increase of $K_2$O contents. The maximum value of the chemical durability was shown in $K_2$$PO_2$$O_{5}$ mole ratio 0.17 when the $SiO_2$ contents were changed, and $K_2$O was fixed at 10 mole%. Hence the change of the $K_2$O/$P_2$$O_{5}$ mole ratio was found that a new main factor of the chemical durability.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.680-689
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• 1996

SrCaCuO와 BiPbCuO 화합물로 이루어진 이중층시료가 만들어 졌으며, 소결과정에서 나타나는 확산과 입자간의 상호작용으로 108K의 임계온도를 나타내었다. 이 시료는 820.deg. C에서 0-210 시간동안 소결되었다. 초전도체의 생성, 성장메카니즘과 임계온도의 관계가 연구되었으며, 최적조건은 820.deg. C에서 210시간 소결하고 SrCaCuO와 BiPbCuO의 도포비가 1:0.6인 시편에서 나타났다. 또한 이중층시료에서 가장 좋은 조성비는 S $r_{2}$C $a_{2}$C $u_{2}$ $O_{x}$와 B $i_{1.9}$P $b_{0.5}$C $u_{3}$ $O_{y}$ 이었다.다.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.714-717
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• 2000

To consider sulfate resistance of cement pastes and motars for 3 types of portland cements which have different $C_3A$ contents an silicate ratio($C_3S/C_2S$), they were immersed in 5% sodium sulfate solution for 400 days. SEM analysis and ($Ca(OH)_2$ contents of cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of ($C_3$ and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of C3A and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement had a good sulfate resistances because of a small quantity of gypsum and ettringite due to less ($Ca(OH)_2$ contents. However, ordinary portland cement had an adverse result. This was also confirmed by SEM analysis.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.41-46
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• 2021

In order to investigate the degree of sewage sludge solubilizaion using ultrasonic(US) combined with calcium peroxide(CaO₂), VSS reduction rate, solubilization rate, SCOD/VSS ratio, SCOD increasing rate, LB-EPS(Loosely-Bound EPS) and TB-EPS(Tightly-bound EPS) were measured. US was compared as a control. Solubilization rate increased by 23.4% under US and increased by 50.7% under US/CaO₂(0.05 g CaO₂/g VSS). and also, at the same conditions, VSS reduction rate increased by 7.1% and 17.7%, respectively. SCOD increasing rate from 10 to 90 minutes was 0.0151 min^-1 under US/CaO₂(0.02 g CaO₂/g VSS). TB-EPS decreased by 36.4% under US and decreased by 59.0% under US/CaO₂(0.05 g CaO₂/g VSS). TB-EPS decreased during first 10 minutes and then decreased slowly until 90 minutes. There was no significant difference in TB-EPS decrease according to the dosage of calcium peroxide.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.359-362
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• 2002

DBPAS has been used to characterize atomic level defect structures in materials. In this investigation the numerical analysis of the Doppler spectra was restricted to the determination of the shape parameter, S, defined as the ratio between the total amount of counts in a central portion of the spectrum and the total amount of counts. As samples were exposed by X-ray increasing from 3, 6, and 9 Gy with 6 MV, and 10 MV each and also by E-beam increasing the energies with 6 MeV, 9 MeV, 12 MeV, and 20 MeV. The S-parameter values were increased as increasing the exposed time and the energies. The S-parameters of the large and small size grains in $CaWO_4$ were measured. The S-parameter of the small size grains in $CaWO_4$ was resulted in larger values.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.20-32
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• 1992

$Na_2O-CaO-MgO-Al_2O_3-SiO_2$ glass was taken as a basic glass and then $Li_2O$ O.5wt%, $K_2O$ 2.0wt% were substituted to $Na_2O$content, MgO 12.0wt %, ZnO 6.0wt % to CaO content. And also nucleation agent $ZrO_2 and $CaF_2$ were added to 1-2wt% respectively. The crystal according to the compositions appeared wollastonite, diopside and diopside.tremolite. The glasses substituted NazO by LizO was decreased thermal expansion coeffcient but substituted by ZnO was opposite direction and both of them increased bending strength. In the ratio of ZrOz to CaF, each 1: 1 and 1: 2 have shown considerable crystal growth at $1000^{circ}C~1050^{\circ}C$ and high bending strength, but the glass in the ratio 1: 2 have shown lowest thermal expansion coefficient. The activation energy was at the glass in the ratio of ZrO, to CaFz 1:2 evaluated 55.24kvsl/mol by Ozawa type and 53.05kal/mol by kissinger type.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.160-161
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• 2005

The $(Sr_{1-x}Ca_x)TiO_3$(SCT) thin films are deposited on Pt-coated electrode (Pt/TiN/$SiO_2$/Si) using RF sputtering method with substitutional contents of Ca. The optimum conditions of RF power and $Ar/O_2$ ratio were 140[W] and 80/20, respectively. Deposition rate of SCT thin film was about 18.75$[{\AA}/min]$. The dielectric constant was increased with increasing the substitutional contents of Ca, while it was decreased if the substitutional contents of Ca exceeded over 15[mol%]. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz].

• Korean Journal of Soil Science and Fertilizer
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• v.2 no.1
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• pp.27-30
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• 1969

The present notes summarize the results obtained from the effect of soil-solution ratio on pH values of soils having widely different physico-chemical characteristics. The pH was determined in deionized water N-KCl and 0.01 M $CaCl_2$ solution The results obtained are: 1. With deionized water, the pH values increase with the increase in soil-solution ratio. The increase is more in upland soils than in paddy soils. 2. With N-KCl solution, there is also an increase in pH values with the increase in soil-solution ratio but the increase is less than the corresponding increase with deionized water. 3. With 0.01 M $CaCl_2$ solution, there is practically no change in pH values with the increase in soil-solution ratio except for saline soils. 4. In case of saline soils, the pH increase even in case of 0.01 M $CaCl_2$ solution with increase in soil-solution ratio, the reason for increase may be due to decrease of electric potential by high concentration of salts.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.78-87
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• 2009

When the steel slag is utilized to the concrete as the alternative fine aggregate, its use is limited as the concrete aggregate because of expansibility caused by much quantity of free CaO. So, this study is intended to examine the characteristics of the concrete which uses the rapidly cooled steel slag whose content of free CaO is sharply reduced by rapidly cooling the steel slag as the fine aggregate. Accordingly, by comparing and considering the results of the concrete slump loss test with the different substitution ratio and fine aggregate ratio of rapidly cooled steel slag, hydration by XRD and SEM analysis, compressive test by age, a length variation test and rapid chloride ion penetration test, the rapidly cooled steel slag's proper substitution ratio and the fine aggregate ratio was derived.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.35-40
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• 1986

The early hydration of tri-calcium silicate $(C_3S)$ with different cooling conditions was studied by varing water/solid ratio and atmosphere. The cooling condition and water/solid ratio affected to the second peak of heat liberation but it had no correlation to the induction period. The $Ca^{2+}$ concentration in the aqueous solution was maximized at the starting point of the second peak of heat liberation but in the $CO_2$ exsistence the $Ca^{2+}$ concentration was low and $SiO_2$ con-centration was increased. The hydration rate of $C_3S$ was so accelerated that the induction period could not appear in the $CO_2$ exsistence.